This invention relates to a dental implant which comprises an implant screw, an implant abutment and a tightening screw. The implant screw has an external thread with which it can be screwed into a jawbone. The implant abutment is joined with the implant screw and attached to the implant screw by the tightening screw. To the implant abutment, a dental prosthesis, a crown, a tooth cap or the like is directly or indirectly attachable or attached. The tightening screw is screwable or screwed into the implant screw. By the tightening screw, the implant abutment is connectable or connected with the implant screw. With a contact surface, the implant screw rests against a contact surface of the implant abutment.
Such dental implant is known from EP 1 529 498 A1. In one embodiment of EP 1 529 498 A1, the implant screw has a conical contact surface and the implant abutment has a conical contact surface complementary thereto. The relative angular position between the implant screw and the implant abutment is not fixed in this embodiment.
Another embodiment from EP 1 529 498 A1 comprises an implant screw which includes an internal hexagon into which a corresponding external hexagon of the implant abutment engages, so that the implant abutment is held in the implant screw secured against rotation and in a predetermined angular position.
From EP 1 269 932 A1 a dental implant abutment with an implant screw made of metal, namely titanium, and an implant abutment made of ceramics is known. The implant screw and the implant abutment are connected with each other by a metallic connecting piece.
From WO 01/50977 A1 another dental implant is known.
WO 2009/009909 A1 discloses a dental implant with an implant screw and an implant abutment, which are screwed to each other and additionally bonded to each other. This adhesive bond leads to considerable shortcomings both in clinical use and as regards the long-term prognosis of the entire system. On the one hand, it is extremely difficult, if not impossible, to reliably remove the leaking excess adhesive after bonding. Such excess adhesive can lead to inflammations at the implant site and consequently to the implant loss. On the other hand, it sometimes is required to again separate the connection between the implant screw and the implant abutment after inserting the restoration, which after adhesively bonding the two components only is possible with difficulty or not at all. Moreover, the durability of an adhesive in the oral environment is only very difficult to predict. Changes in temperature, fluctuations of the pH value, mechanical loads and moisture lead to rapid aging in particular of formerly plastic materials.
DE 101 29 684 B4 shows another dental implant.
The design of the implant screw and/or the implant abutment can lead to the fact that with certain materials, in particular with ceramics or a ceramic-like material or a material which contains ceramics or a ceramic-like material, but also with materials which contain plastics, extensive material accumulations are present in various regions of these components. Due to these different volumes of material it can occur that the finished component is not sufficiently dimensionally accurate. This risk in particular exists when the manufacturing method includes a shrinking process, as is the case in particular when sintering ceramics or materials containing ceramics, but possibly also with materials which contain plastics. In general, the shrinking process does not proceed linearly in particular during sintering. The material of the implant screw and/or the implant abutment thus each can shrink to a different extent in various regions of these parts corresponding to the different volumes of material. When the implant screw and the implant abutment are joined and braced with each other by the tightening screw, it is therefore not possible to achieve a completely stressfree form fit of the joined surfaces. This results in a risk of fracture and/or the risk of a lack of bacteria tightness. These risks also can result from a surface roughness of the material independent of the shrinking process mentioned above.
In experiments known from the prior art, ceramic contact surfaces have led to far-reaching problems. Production-related inaccuracies, even in the micrometer range, have led to the occurrence of force and stress peaks in the material during the introduction of forces. Other than in metallic components, which have a certain elasticity or ductility due to the material used, ceramic materials are brittle, hardly elastic and more or less not deformable. With the manufacturing methods employed so far, the accuracy of the connection merely could be increased to a certain degree. In microscopic terms, however, this cannot be referred to as a “flat, homogeneous” contact surface. So far, the same rather is present sporadically, approximately comparable to a sand grain under a glass plate lying flat on a surface. This results in stress peaks and resulting fractures of one or both components already with physiologically occurring chewing forces.